An image forming apparatus including an image forming unit for forming an image on a sheet, a plurality of trays each holding sheets on which the image is formed by the image forming unit, and a feed unit for feeding sheets held in any one of the trays to the image forming unit has been conventionally proposed. In such image forming apparatus, it is possible to form an image on a sheet by feeding sheets held in any one of the trays each holding sheets to the image forming unit by the feed unit. Further, in such image forming apparatus, there has been proposed that a unit for detecting the size and kind of sheet held in a tray is provided and, when the size and kind of sheet is designated by an upper apparatus, an image is formed by automatically selecting the tray holding sheets of the designated size and the kind and feeding the sheet (for example, see JP-A-2-182632).